Normally if they want more volume I'll give it to them,
music only.
Far as them singers who want you to turn it up so they can be heard? Sure why not? Turn the music down and let them see how good they are, singing mostly acapella. I have done all of the above with obnoxious drunks (non regulars) being a pain.
If they are regulars and only a pain now and then I cut them a break, tweak them properly, let their friends tell them how good they were
Most of my regular singers, I give them as many tweaks as I can to make them sound better. Double, Echo, Kick the bass back, crank the music.